Fretboard with notes
The fretboard (also called fingerboard) is the top part of the neck on a guitar, between the body and the headstock. On the diagram below you can learn all the notes on the guitar fretboard - after the 12th fret it's all repeating again (i.e. the 13th fret is the same as the 1st, only one octave higher).
It's important for your development as a guitar player to learn the position of every note. This helps the understanding of chord theory and makes it easier to play melodies, solos and licks.
It starts with the open strings, when continues with the notes on fret 1 to 12.
The fretboard on the guitar illustrated. After the 12th fret it's all repeating again.
In the fretboard diagram, C# (C sharp) is used and not Db (D flat), which follows for the rest of these situations as well. If you for example are looking for the note Ab (A flat) this is the same as G# (G sharp).
Learning the fretboard - note location
To memorize the fretboard and note for note is not necessary. An easier way is to recognize the pattern that is repeating and learn some notes to use a reference. For example, when you know that the lowest string on the fifth fret is A you could find another A two strings up and to frets to the right. The same method can be used for the fifth-third string. For example, when you know that the next lowest string on the fifth fret is D you could find another D two strings up and to frets to the right. Keep looking at the note locations and you will find more patterns.
The story behind the dots
Between some of the frets are inlays, most often displayed with dots. These function is to help you to orient in the horizontal direction and making it easier to find the right fret fast. The inlays on the fretboard are placed schematic on guitar and the typical formation involves single dots on the 3rd, 5th, 7th, 9th, 15th, 17th, 19th, 21st frets and double dots on the 12th and 24th frets (the reason for double frets on 12th and 24th frets are because the notes starts over on these frets: the notes on 12th fret are one octave higher than on the open strings, and the notes on 24th fret are one octave higher than the notes on 12th fret).
On the guitar fretboard the same note is represented many times, seven to eight times to be precise. Some of the notes are in different octaves. For example, the C note is represented seven times on the first twelve frets. If we start counting from the left on the lowest string the first two C notes are in one octave, the next three are in a second octave and the last two in a third octave.
If you find it very difficult to learn all the notes on the fretboard, you should at least start by learning the tones on the low E and the A strings because the roots of chords are often on these strings. As you can observe, the lowest and the highest strings are identical.
Fretboard note decals
If you still are uncertain there are ways to get around. For example, you could tape some notes on the side of the guitar neck or, if you want it to be a little fancier, you could use special made note decals
as in the picture below.